[Fix] Ignore commented profile source lines

[Vaibhav-C-S]

Fixes: #1889

This updates the install script so commented-out nvm profile lines are not treated as active setup lines.

Before this change, install.sh checked for /nvm.sh and $NVM_DIR/bash_completion anywhere in the profile file. This also matched commented-out lines as well.

# [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
# [ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"

As a result, reinstalling nvm skipped appending active setup lines. After opening a new bash shell with that profile, nvm was still unavailable:

$ nvm --version
bash: nvm: command not found

After this change, the installer ignores commented-out setup lines and appends active nvm and bash_completion lines:

=> Appending nvm source string to ~/.bashrc
=> Appending bash_completion source string to ~/.bashrc

Hence, nvm is available as expected:

$ nvm --version
0.40.5

[Vaibhav-C-S]

Hi @ljharb , can you please look at this pr, when you have time, it is a small and focused fix.

[ljharb]

Thanks! This will need regression tests, though.

[ljharb]

This still matches indented comments - [[:space:]]* backtracks, so [^#] can itself match a space: a line like # [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" (or a tab-indented one) is still treated as active, and the #1889 repro persists for it.

Excluding whitespace from the guard class fixes it without breaking indented active lines:

'^[[:space:]]*[^#[:space:]].*/nvm\.sh'

(the $NVM_DIR/bash_completion pattern below has the same issue)

The regression tests should include an indented-comment case, since that is the case that distinguishes this pattern from the correct one.

[Vaibhav-C-S]

Thanks @ljharb will work on the regex fix and will add regression tests.